Primary sarcomas of the lung are exceedingly rare. They usually represent cases of fibrosarcoma, leiomyosarcoma, and hemangiopericytoma. Less commonly synovial sarcoma, malignant peripheral nerve sheath tumor, malignant fibrous histiocytoma and osteosarcoma have been described. Primary pulmonary myxoid leiomyosarcoma has only been reported once presenting as a peribronchial mass (1). However, myxoid leiomyosarcoma arising in other sites including the pulmonary vein (2) has been reported. We report a case of primary myxoid leiomyosarcoma presenting as a loculated pleural effusion.
A 71 year old non-smoking female presented with left shoulder pain. Her medical history was only remarkable for a hysterectomy performed 20 years ago with pathologic findings consistent with leiomyomas. On initial evaluation a chest X-ray (Figure 1) and a CT scan of the chest revealed a loculated right pleural effusion. No parenchymal abnormalities were observed. A bone scan was performed which demonstrated enhancement of the pleural effusion with no skeletal abnormalities. A thoracocentesis yielded exudative fluid with negative cytology. A closed pleural biopsy was nondiagnostic. Subsequently, the patient underwent a thoracotomy. Frozen section revealed malignant cells and a right lower lobectomy with mediastinal lymph node dissection was performed. A mass measuring 15.0 x 14.5 x 7.0 cm. composed of soft mucoid material was identified in the lung parenchyma extending to and involving the visceral pleural. Microscopically, this lesion was composed of spindle cells surrounded by a loose myxoid stroma (Figure 2) with focal hypercellular areas dysplaying a fascicular pattern.Immunohistochemical stains were positive for smooth muscle actin (SMA)(Figure 2 - insert), muscle specific actin (MSA), desmin, and vimentin. Electron microscopy revealed plaques, thin filaments and dense bodies. All resected mediastinal lymph nodes were negative for tumor. The postoperative course was unremarkable. The patient was offered but declined postoperative chemotherapy. She has remained clinically free of recurrence one year following thoracotomy.
Primary myxoid leiomyosarcoma of the lung is an extremely rare entity with only one previously reported case (1). Radiologically, myxoid leiomyosarcomas usually appear as sharply demarcated masses with homogeneous density. We present a case in which no mass could be identified by plain film or CT imaging. The mucous character of the neoplasm combined with the presence of pleural involvement precluded the preoperative identification of parenchymal involvement. Frequently conventional pulmonary leiomyosarcoma is diagnosed by fine needle aspiration cytology (3). Although in the present case there was spillage of mucinous matrix into the pleural cavity, aspiration cytology failed to identify neoplastic cells. This histologic variant is known to be deceptively hypocellular with lower mitotic rates as compared to conventional leiomyosarcomas. Despite their hypocellularity, extrapulmonary myxoid leiomyosarcomas tend to behave aggressively with a high rate of local recurrence. This case does not follow this pattern. Despite a large primary tumor with pleural involvement the patient has shown no evidence of recurrence one year following resection.
We describe the second case of primary myxoid leiomyosarcoma of the lung reported in the medical literature. Our patient’s course following resection has been distinctly superior to that reported with myxoid leiomyosarcomas of extrapulmonary origin. The role of adjuvant chemotherapy and radiation therapy remains uncertain.
J.I. Mora, None.